Pilot gas alarm

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sailor211

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We have a pilot gas alarm with two sensors. When I go to the boat and switch the power on, powering up the alarm, The alarm goes off. Up till last time turning the unit off and rebooting solved the problem. Now the alarm keeps going.

There is no gas, it's turned off at the bottle, so what do they detect?
Can I do anything other than replacing the sensors at the cost of £80:-. Would blasting them with compressed air get mould / dirt out of the sensors to keep them going.
 
Be gentle with the sensors if they are not already knackered. Blasting with air sounds a bit aggressive to me.
Not sure about Pilot, but some used to be a heated (electrically) wire that glowed brighter in gas and thus changed it's resistance which triggered the alarm circuit. A good air blast could blow away the element... Problem is, what is making it apparently drop in resistance? - contamination from something conductive? Perhaps they are measureable against a known good resitance.
Just Googled and found this http://www.figaro.co.jp/en/item2.html so I was over-simplifying things, perhaps a check of the cable and connections may reveal something?
Try comparing the resistance (forward and backward) between the two sensors you have. Then try disconnecting one or swapping them to find out which bilge appears to have the problem - maybe there IS a problem.....
If it only (and always) fails when you return to the boat after a rest period, try leaving the bottle on deck (padlocked to the mast if you must) while you are away and see if the problem persists.
 
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These sensors are easily damaged by moisture. Don't know where your sensors are, but this could be the cause. You could try cleaning them, but I suspect you'll end up replacing them. There are gas alarm systems with waterproof sensors - Google for nereus waterguard.
 
Mine also does this. I think it is a fairly common problem with the Pilot sensors. I sometimes have to turn the power on/off more than 10 times if I have been away from the boat for a while. The alarm beeps for 30 secs then sounds continuously. I then turn the power off start again. Sometimes one sensor works before the other. If I'm cruising and the power has only been off for a few hours, the alarm behaves itself. I'm not sure why it does this but it is a nuisance. I replaced the sensors once and that solved the problem but only temporarily.
 
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Dipper said:
Mine also does this. I think it is a fairly common problem with the Pilot sensors. I sometimes have to turn the power on/off more than 10 times if I have been away from the boat for a while. The alarm beeps for 30 secs then sounds continuously. I then turn the power off then start again. Sometimes one sensor works before the other. If I'm cruising and the power has only been off for a few hours, the alarm behaves itself. I'm not sure why it does this but it is a nuisance. I replaced the sensors once and that solved the problem but only temporarily.
Click to expand...

How do you know that it's not warning you of a gas leak?
 
Dipper said:
Mine also does this. I think it is a fairly common problem with the Pilot sensors. I sometimes have to turn the power on/off more than 10 times if I have been away from the boat for a while. The alarm beeps for 30 secs then sounds continuously. I then turn the power off then start again. Sometimes one sensor works before the other. If I'm cruising and the power has only been off for a few hours, the alarm behaves itself. I'm not sure why it does this but it is a nuisance. I replaced the sensors once and that solved the problem but only temporarily.
Click to expand...


I have not had to switch on off for ten times, but once or twice, maybe I have to persevere.

Damp may be the problem.

It is expensive if I replace the sensors and it only solves things temporarily. I do noy want to turn it off and use the bypass valve.
 
sailor211 said:
I have not had to switch on off for ten times, but once or twice, maybe I have to persevere.

Damp may be the problem.

It is expensive if I replace the sensors and it only solves things temporarily. I do noy want to turn it off and use the bypass valve.
Click to expand...

This is a serious question, in your original post you said "When I go to the boat and switch the power on, powering up the alarm, The alarm goes off." How do you know it's not detecting gas? Surely turning the power on and off is potentially dangerous, due to the possibility of sparks igniting gas vapours.
 
pvb said:
This is a serious question, in your original post you said "When I go to the boat and switch the power on, powering up the alarm, The alarm goes off." How do you know it's not detecting gas? Surely turning the power on and off is potentially dangerous, due to the possibility of sparks igniting gas vapours.
Click to expand...

Good point. In my case, the fault light comes on so it's not detecting gas. Surprisingly, the Pilot user manual says the alarm does go through the stabilisation period (the intermittent beeping) before it sounds an alarm.
 
sailor211 said:
I have not had to switch on off for ten times, but once or twice, maybe I have to persevere.

Damp may be the problem.

It is expensive if I replace the sensors and it only solves things temporarily. I do noy want to turn it off and use the bypass valve.
Click to expand...

I got so fed up with turning the battery switch on/off that I've fitted a separate switch for the alarm (left in the on position) which is easier to operate. Check yours has the 'fault' light on when it sounds continuously or (as pvb mentioned) it may be gas.

I did begin to wonder if the unit had an internal battery that needed recharging but I don't think it does.
 
pvb said:
This is a serious question, in your original post you said "When I go to the boat and switch the power on, powering up the alarm, The alarm goes off." How do you know it's not detecting gas? Surely turning the power on and off is potentially dangerous, due to the possibility of sparks igniting gas vapours.
Click to expand...

This is part of the problem. Separate gas locker vented over the side. When i Leave the boat, i shut the solenoid. Turn the gas of at the bottle. Burn off the remaining gas in the pipe, shut the local valve.

Not much source for the gas to get into the cabin.

Arrive turn on the unit , test sequence starts alarm and goes continuous. Turn off and reboot alarm stops. Turn gas on at bottle, switch on solenoid, open local gas tap. Put on kettle. Because the alarm is be rebooted then does not detect gas I assume that a start up alarm is a fault not gas. One day it might be, if I do not turn off the gas and shut the valves.

I have not tested the alarm by filling the cabin with gas!! And will not.

I could say that the gas safe installer sold me something that is not fit for marine useage.

If I leave the unit on all the time and the alarm triggers falsely will it flatten the batteries with a fortnights continuous running?
 
I had the same problem. My boat was for Skippered charter, so a alarm was mandatory. I had the boat for 12 years and found the alarm became 'skittish' (like yours) after about 5 years. It was inclined to go off when a 2t outboard came by and always when the boat had been unoccupied for any time. I solved the problem (Twice!) by getting a new transducer.
 
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